Thread transporting drive



Dec. 27, 1966 SCHMIDT ETAL THREAD TRANSPORTING DRIVE Filed Sept. 11,1964 FIG. 7

FIG. 2

FIG. 4

FIG- 6 z ZM at #14 Z 4 fr 3 AME 7 J United States Patent 3,294,328THREAD TRANPORTENG DRIVE Richard Schmidt, Stuttgart-Vaihingen, and HansJoachim Stock, Freiburg im Breisgau, Germany, assignors to Franz MaratG.m.h.H., tnttgart-Vaihingen, Germany Filed Sept. 11, 1 364, Ser. No.395,799 1 Claim. (Cl. 242-47.01)

The present invention relates to a thread transporting drive, and moreparticularly to an apparatus for rotating a thread transporting rollerof the type used in knitting machines for supplying threads at theknitting stations of the machine to the knitting needles.

A thread is guided, or wound in several windings, about a cylindricaltransporting roller which has a hard surface of mirror-like smoothness.If slippage of the thread on the transporting roller is desired, thetransporting roller is rotated at a very high speed which is a multipleof the highest possible thread transporting speed, and the thread slipson the roller surface when a greater or smaller amount of thread isrequired for a particular loop knitted by the knitting needles of themachine.

For other knitting operations, the thread must be posi tivelytransported without any slippage, and in this event, the thread is Woundin several turns about the transporting roller which is rotated at sucha speed that the thread is delivered at a constant speed to the knittingneedles.

Thread transporting rollers serving this purpose are provided at theseveral knitting stations of a knitting machine, for example on acircuit knitting machine, and are driven by a gear transmission,friction transmission, or pulley and belt transmission. Suchtransmissions be tween the prime mover and the thread transportingrollers cause irregularities of the roller motions which have adetrimental effect on the uniform transport of the thread due to thefact that the thread reacts to the smallest differences betweenfrictional forces present between the thread and the surface of theroller. Particularly the necessary uniform tension of the thread isimpaired if the rotary speed of the transporting roller fluctuates evenslightly, or if the shaft of the transporting roller is caused towebble.

It is one object of the present invention to overcome the disadvantagesof known thread transporting drives, and to provide a drive for a threadtransporting roller which assures a smooth and uniform rotation of atransporting roller at a constant speed.

Eddy current couplings are known for the transmission of power. Sucheddy current couplings assure a very smooth transmission of the rotarymotion. However, the eddy current couplings which are used for otherpurposes provide a driving part and a driven part mounted on a commonshaft. In this manner, irregularities and fluctuations of the rotaryspeed are eliminated due to the effect of the eddy current coupling, buttransverse motions of the drive shaft, such as wobbling, are transmittedto the driven coupling part, and if such an eddy current coupling wouldbe used for driving a thread transporting roller, the roller wouldwobble with the drive shaft so that the thread would not have uniformtension at all times while being transported.

It is another object of the invention to overcome this disadvantage ofeddy current couplings, and to provide a drive arrangement for a threadtransporting roller in which irregular transverse motions of the driveshaft are not transmitted to the thread transporting roller.

Another object of the invention is to provide a thread transportingroller rotating at a constant speed about a true axis whose positiondoes not change.

With these objects in view, a thread transporting drive according to theinvention comprises a first shaft and a second shaft spaced in axialdirection along a common axis, and an eddy current coupling includingtwo coupling halves respectively secured to the shafts and connectingthe same for rotation.

One of the shafts is a drive shaft which drives the other shaft throughthe eddy current coupling. The thread transporting roller is secured tothe other shaft and due to the fact that the drive shaft and drivenshaft are in no way mechanically connected, irregular motions of thedrive shaft are not transmitted to the thread transporting roller, or toa thread transported by the same.

One coupling half includes a magnet and the other coupling half includesa good electric conductor so that strong eddy currents are produced. Itis advantageous to provide a further member of good magneticconductivity on the side of the electrical conductor remote from themagnet so that a strong closed magnetic field passing through theelectrical conductor is assured.

The thread transporting drive according to the present invention has theadvantages of an eddy current coupling, namely immediate establishing ofthe coupling connection, and a smooth coupling engagement withoutmechanical parts, without the disadvantages which would be caused bymounting both coupling halves on the same shaft. In this way, a driveconnection results which is particularly suited for thread transportingrollers in knitting machines.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claim. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIG. 1 is a fragmentary schematic elevation, partially in section,illustrating one embodiment of the invention;

FIG. 2 is .a fragmentary schematic elevation, partially in section,illustrating another embodiment of the invention;

FIG. .3 is a fragmentary schematic elevation, partially in section,illustrating a third embodiment of the invention;

FIG. 4 is a schematic side view taken on line 4-4 in FIG. 3;

FIG. 5 is a fragmentary schematic elevation, partially in section,illustrating another embodiment of the invention; and

FIG. 6 is a sectional view taken on line 66 in FIG. 5.

Referring now to the drawing, and more particularly to FIG. 1, a driveshaft 1 is driven by the drive means of the knitting machine, not shown,through a pair of meshing bevel gears 3 and 2. Bevel gear 2 is securedto shaft 1, and bevel gear 3 is coaxial with the main axis of a circularknitting machine and has a great diameter, so that a bevel gear 2 can beprovided at each knitting station spaced around the periphery of theknitting machine. It will be understood that a thread transporting driveof any embodiment of the invention is provided at each knitting station.

Drive shaft 1 is mounted in a hearing In to which a horseshoe magnet :issecured. Magnet 6 has two terminal poles disposed adjacent to a circulardisc 7 which consists of a material which has a high electricconductivity. Dis 7 is secured to a second shaft 8 mounted in a bearing14 coaxially with a drive shaft 1 and axially spaced from the same. Atransporting roller 10 is secured to shaft 14 and has a smoothcylindrical surface about which a thread 20 is looped in at least oneturn. Intermediate the electrioally conducted disc 7 and transportingroller 10, another circular disc 9 consisting of a magnetizable materialof high magnetic conductivity is secured to shaft 8 for rotationtherewith. Discs 7 and 9 may actually be secured to the transportingroller 10, and disc 9 may be integral with transporting roller 10, inother words, transporting roller '10 may consist of a highlymagnetizable material.

The magnetic field of magnet 6 passes through the magnetizable materialof member 9 and permeates the electrically conductive disc 7 so thateddy currents are produced in disc 7 during rotation of magnet 6 andproduce a magnetic torque by which transporting roller 10 is rotated insynchronism with magnet 6 so that thread 20 is transported. Themagnetizable disc 9 may be omitted but improves the efiiciency of thecoupling.

The embodiment of FIG. 2 includes a pulley 4 secured to drive shaft 1and driven by belt '5 from the drive means of the knitting machine, notshown. A horseshoe magnet 6 is secured to shaft .1 and rotates with thesame. Shaft 1 is extended between the legs of the magnet, and carries acore member 11 of cylindrical shape which rotates at the same speed asmagnet 6 and consequently has its ends always located opposite the polesof magnet 6 and forming two terminal gaps with the same through whichthe magnetic field lines pass. A pot-shaped member 12 consisting of amaterial having good electric conductivity is secured to a shaft 13spaced in axial direction from shaft 1 along a common axis. A bearing 14supports shaft 13, and a thread transporting roller 15 is secured toshaft 13 on the other side of. bearing 14. The cylindrical portion ofthe pot-shaped member 12 is located in the two terminal gaps between theend of core member .11 and the poles N and S of magnet 6. When shaft 1is driven by the transmission 4, in synchronism with the operations ofthe knitting machine, magnet 6 rotates together with core member 11, andthe magnetic field passing through the two gaps and core member 11produces eddy currents in the pot-shaped member 12 so that a magnetictorque develops which couples member 12 to the magnetic means 6, 11whereby shaft 13 and transporting roller 15 are driven in synchronismwith shaft .1 to transport a thread, not shown, wound about thecylindrical surface of roller .15. In a modified embodiment transportingroller 15 is omitted, and the cylindrical surface of pot-shaped member12 which projects from the magnetic means transports the thread which iswound about the cylindrical portion of member 12 as shown in FIG. 1. Theaxial length of the cylindrical part of member 12 may be increased forthis purpose, as compared with the illustration of. FIG. 2.

In the embodiment of FIG. 3, drive shaft 1 is driven from the knittingmachine as described with reference to FIGS. 1 and 2 and carries amagnetic bar 16. The driven shaft 18 is mounted in a bearing 14 andfixedly carries a pot-shaped member 19 which consists of amaterialhaving high magnetic conductivity so that the magnetic fieldlines pass from the poles of magnet 16 through the magnetizable member.19, as indicated by broken line 611. A pot-shaped member 17 consistingof a good electrical conductor is fitted into the interior of thepot-shaped member 19 and secured to the same and to shaft 14.Consequently, the magnetic lines of force 601 permeate the portions ofmember 17 located opposite the poles of magnet 16 and produce eddycurrents in the same during rotation of shaft 1 with magnet 16. Themagnetic torque developed in this manner couples member 17 to magnet 16so that shaft 18 is rotated in synchronism with shaft 1. A thread, notshown, is wound about the smooth cylindrical surface of member .19 whichserves as transporting roller. However, it is also possible to secure atransporting roller to shaft 18, as explained with reference to FIG. 2.

In the embodiment illustrated in FIGS. 1-3, the elements rotating withthe driven shaft, namely the transporting roller and the driven parts ofthe eddy current coupling must be dimensioned in such a manner that themoment of. inertia is sufficient in relation to the magnetic couplingforce to compensate and equalize forces transmitted from thedriven shaftor caused by the thread. The parts rotating with the driven shaft andmoving in synchronism with the transported thread should have asubstantial mass to equalize fluctuating forces. This can beaccomplished by mounting the heavier parts of the magnetic coupling onthe driven shaft.

In the embodiment of FIGS. 5 and 6, the drive shaft 1 carries only apot-shaped member 23 which consists of a material having high electricconductivity. The driven shaft 24 carries the heavy magnet 21 which hasits ends located spaced a short distance from the cylindrical innersurface of member 23. The driven shaft 24 also carries pot-shaped member22 which consists of a material having high magnetic conductivity. Thecylindrical part of member 22 surrounds the cylindrical part of member23 and is spaced from the same by an annular gap. The magnetic field ofmagnet 21 is closed through pot-shaped member 22 as indicated by brokenline 6a and the magnetic field lines permeate the cylindrical portion ofpotshaped member 23. During rotation of shaft 1 with member 23, the eddycurrents produced by magnet 21 in member 23 produce a coupling torque bywhich magnet 21 and pot-shaped member 22 are coupled to the rotatingmember 23 whereby shaft 24 is driven. In the embodiment of FIGS. 5 and6, the two heavier parts of the eddy current coupling are mounted onshaft 24, while in the embodiment of FIGS. l-3 the heavy magnet ismounted on the drive shaft 1. Due to the great inertia of parts 21, 22,24, fluctuations in the rotary speed are equalized, and a thread woundabout the outer cylindrical surface of pot-shaped member 22 istransported at a uniform speed. It is, of course, also possible tosecure a transporting roller to shaft 24 on the right side of bearing14, as viewed in FIG. 5.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofthread transporting drives differing from the type described above.

While the invention has been illustrated and described as embodied intwo terminal coupling halves of an eddy current coupling mounted on twoterminal spaced coaxial shafts, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claim.

What is claimed as new and desired to be secured by Letters Patent is:

A thread transporting drive comprising, in combination, a first shaftand a second shaft spaced in axial direction along a common axis; drivemeans for driving said first shaft; and an eddy current couplingincluding a magnet secured to said first shaft for rotation therewith, apotshaped transporting roller having a magnetizable cylindrical portionadapted to be engaged by a thread and surrounding said magnet so as toform two gaps with the same, and a circular bottom portion having acenter secured to said second shaft for rotation therewith, and apot-shaped member consisting of a material having high electricconductivity fitted into the interior of said potshaped transportingroller and having a cylindrical portion located in said gaps so that amagnetic field passing through said transporting roller permeates saidcylindrical 5 portion of ,said pot-shaped electrical conductive memberwhereby said first and second shafts are coupled to each other in such amanner that irregular motions of said first shaft are not transmitted tosaid thread transporting roller and to a thread transported thereby.

References Cited by the Examiner UNITED STATES PATENTS 1,892,554 12/1932Kellogg. 2,902,612

FOREIGN PATENTS FRANK I. COHEN, Primary Examiner.

9/1959 Whearley 310105 10 W. S. BURDEN, Assistant Examiner.

